This invention relates generally to plastic components and more particularly to plastic corner components for static structures and methods of making such components.
Today, a variety of different thermoplastic materials simulating naturally occurring materials such as marble, stone, wood, etc. are utilized in the interior of homes, offices and other buildings for counters, shower stalls and the like. The thermoplastic materials used in these applications are selected from the group consisting of filled acrylics, filled polyesters and filled acrylic-polyester blends. These materials are sold under various trademarks, such as the Registered Trademark CORIAN of E. I. DuPont de Nemours Company, the trademark GIBRALTER of Wilson Art Company, the Registered Trademark FOUNTAINHEAD BY NEVAMAR of the Nevamar Corporation, the trademark CERELL of the Formica Corporation, and the Registered Trademark AVONITE of the Avonite Corporation.
The aforementioned filled thermoplastic materials are manufactured in square sheets varying in thickness. The square sheets can be fabricated in any thickness from 4 mm up, however, they are typically available in 1/4 inch, 3/8 inch, 1/2 inch and 3/4 inch thicknesses.
Many of the filled thermoplastic materials possess functional and cosmetic properties which make their use desirable in kitchen and bathroom applications such as kitchen counter-tops, bathroom vanities, shower stalls and other components having corners.
For example, the aforementioned filled thermoplastic materials are presently used to fabricate counter-top features such as a backsplash and/or a front drip edge. Each of these features forms a corner on an existing counter-top surface in order to contain splashed water and protect surrounding walls and cabinets. These materials are also used to fabricate shower floor pans. Such floor pans are typically designed with cornered side walls for containing water. Similarly, filled thermoplastic materials have been used to fabricate corner sections of the shower stalls. These corner sections join the shower walls together.
Presently, a corner component, such as a backsplash or a front drip edge, is fabricated of filled thermoplastic materials by adhesively joining a strip of such material to a counter-top made of the same material. Similarly, the corner components contained in shower floor pans and corner sections are often fabricated by joining together two pieces of the filled thermoplastic material.
The fabrication and assembly of such corner pieces thus requires considerable time, effort and expense. For example, to form a backsplash or a front drip edge, at least two pieces of material must be cut from a flat sheet of filled thermoplastic material--one piece for the counter-top deck and another piece for the backsplash and/or front drip edge. Once placed in position, the backsplash piece or front drip edge forms a right-angle corner with the counter-top deck. Next, clamping tools and braces are attached to orient and hold in place the counter-top deck and the backsplash piece or front drip edge while adhesive is applied and allowed to dry.
Similarly, in forming shower wall corner sections and floor pans which are utilized in the construction of shower stalls, the present method of fabrication utilizes plural components which must be secured together using adhesive. Prior art methods of forming shower stall corner sections and shower floor pans do not make use of a bent corner of unitary or one-piece construction.
While the foregoing prior art corner components and methods of forming same may achieve their intended structural purpose, these corner components and methods for making the same nevertheless leave much to be desired from various standpoints. In this regard the process of securing together, e.g., gluing, the multiple components to form the corner is labor intensive, requires special techniques, and is time consuming. Moreover, corner sections comprised of plural adhesively secured components may be prone to leakage where the two or more pieces are joined together if the joint is not a good one. Perhaps, most importantly, is the fact that a corner section fabricated from plural components is not as aesthetically pleasing as one of a unitary, i.e., one-piece, construction since the later type of corner does not include any seam line.
For some applications filled thermoplastic materials can be formed into integral corner members by a method known as thermoforming. This method entails heating and bending the material into the corner. For example, a technical bulletin published by E. I. DuPont de Nemours Company entitled "Thermoforming Sheets Of CORIAN.RTM." describes this method. In thermoforming, a sheet of thermoplastic material is cut to finished dimensions and heated in a typical convection oven to a temperature between 275.degree. F. and 325.degree. F. Heat up times vary depending on the heater design and the size of the piece to be formed. The heated thermoplastic sheets are thereafter mechanically formed or bent into desired shapes and allowed to cool.
When bending a heated sheet of filled thermoplastic material, a minimum bend radius must be maintained. This minimum bend is usually recommended by the manufacturer. For example, in its technical bulletin DuPont recommends that for a 1/4 inch CORIAN.RTM. sheet a bend radius of no less than 1 inch must be maintained. Similarly, for 1/2 inch CORIAN.RTM. a bend radius of no less than 3 inches must be maintained and for 3/4 inch CORIAN.RTM., a bend radius of no less than 5 inches must be maintained. Bending thermoplastic sheets to a radius smaller than the recommended value can result in whitening, crazing, cracking, or reduced impact resistance. As can be appreciated from the foregoing technical information, under this method of thermoforming, a smaller bend radius can be achieved by using thinner thermoplastic sheets. Conversely, when thermoforming thicker stock, a larger bend radius must be maintained to avoid the aforementioned problems. The present process of thermoforming requires exposure to temperatures where discoloration may take place due to exposure to heat over an extended period of time. By utilizing thinner stock thermoplastic sheets, pliability is achieved in a lesser period of time thus reducing the possibility of discoloration.
In many applications, such as the construction of counter-tops, shower stall corner sections, and shower pans, for both cosmetic and functional reasons it is desirable to form corners that have a bend radius which is much smaller than that recommended by the manufacturer for given material thicknesses. Therefore, the foregoing prior art method of thermoforming is unavailable, and the only way to fabricate such corner sections heretofore has been by joining separate components together, as described above, with all of the attendant disadvantages.
For example, in fabricating counter-tops with backsplash and front drip edge features, it is desirable to use a thermoplastic sheet which is 1/2 inch in thickness to assure proper impact resistance and shock absorption. In forming a backsplash or front drip edge from thermoplastic material of sufficient thickness, for cosmetic reasons it is desirable to achieve a tight radius bend, such as no greater than 3/8 inch. The tightest bend radius which is recommended under present thermoforming methods for 3/8 inch thick CORIAN.RTM. material is somewhere between 1 inch and 3 inch.
Therefore, under present methods, thermoforming is unavailable for fabricating these features in a counter-top because one cannot achieve a suitably tight bend radius in thermoplastic materials of thickness necessary for counter-top fabrication.
For similar reasons, the prior art method of thermoforming is unavailable for bending thermoplastic sheets to form sidewalls of shower pans. To assure a snug fit between the shower pan sidewalls and shower walls which are inserted therein, it is necessary that the sidewalls be bent at a tight bend radius no greater than 3/8 inch radius. This is not possible under the present method of thermoforming where shower pans must be comprised of thermoplastic material 1/2 inch in thickness or greater for weight bearing ability.
Similarly, the prior art method of thermoforming is unavailable for creating shower stall corner sections. Typically, shower stall corner sections are at least 1/2 inch in thickness. To assure a proper fit with shower walls it is desirable to form the right-angle corner sections by bending a flat thermoplastic sheet to a radius of no more than 3/8 inch. Since manufacturers recommend that 1/2 inch thick thermoplastic sheet be bent no less than a 3 inches radius, the prior art method of thermoforming is inappropriate for forming shower stall corner sections.
Therefore, in the previously mentioned applications and in other applications, there is a need for corner components of one piece construction that have a tight bend radius and for methods of making the same.